1. Field of the Invention
The invention relates to a fluid operated position regulator for power devices and in particular for process valves, comprising a regulator housing, in which at least one servo means, which is able to be shifted by controlled fluid actuation with the performance of a positioning movement, is arranged, said servo means being able, in a fashion dependent on its position, to place, in different manners, a supply opening, a venting opening and a power connection provided for the connection of the power device, in a fluid circuit with each other.
2. Description of the Related Art
A position regulator disclosed in the European patent publication 0 726 511 B1 of this type comprises a servo means arranged in a regulator housing which is in a position of connecting a power connection in a manner dependent on the assumed position selectively with a supply connection or a venting connection or simultaneously disconnecting them from both of them. It is in this manner that the fluid pressure available at the power connection, which is for example employed for the actuation of process valve or some other power device, is able to be set in accordance with requirements. The position, dictating the current switching state, of the servo means may be influenced by an adjustable control pressure, which acts on a diaphragm element of the servo means in a manner opposite to a mechanical spring means. Since the position regulator is so designed that the servo means assumes the venting position in the case of a control pressure being equal to the pressure of the surroundings, it is relatively difficult to exactly so set the control pressure that there is a closed state separating the power connection simultaneously from the two other connections and entailing a constant position of the power device which is connected.